(Bloomberg) -- European diplomats have moved to seize back the initiative on one of their continent’s most intractable fronts after U.S. efforts under President Donald Trump for a diplomatic victory unraveled last month.

It’s the latest salvo between the U.S. and the European Union in the Balkans, where officials have accused the Trump administration of freezing them out of talks between Serbia and Kosovo that were to culminate in a White House meeting between the leaders.

That June 27 summit fell apart after the president of Kosovo, Hashim Thaci, was accused of war crimes just days before. Now, Chancellor Angela Merkel and French President Emmanuel Macron will join the leaders of Serbia and Kosovo in a video conference Friday, with an EU summit planned two days later in a bid to resuscitate the stalled efforts.

The EU needs to wrest control over the Balkan diplomacy and can’t afford to surrender a key matter of European interests to the U.S. as Serbia and Kosovo both seek a path to join the 27-member bloc, according to four officials familiar with the discussions. U.S. special envoy Richard Grenell says he supports the EU initiative.

For the last decade, the Greek debt crisis, Brexit and now Covid-19 have fueled resistance among some of the bloc’s more established members toward letting both its poorer ex-communist newcomers and those waiting for membership deeper into the fold.

That’s given the U.S., Russia and China an opening to increase their influence in the region. But there are signs that reluctance may be easing.

In March, EU governments unblocked the membership path for North Macedonia and Albania by overcoming a French roadblock after months of deliberations. And Croatia, another country that emerged from the wars that broke up the former Yugoslavia in the early 1990s, will peg its currency to the euro in the coming days along with fellow EU newcomer Bulgaria -- a step they consider vital to joining the richer West.

Serbia and Kosovo have made much less progress in their accession efforts, in large measure due to a standoff following a 1998-1999 war that led to the latter declaring independence in 2008. There’s no compromise in sight as both nations stick to their positions while grappling with political challenges at home. Kosovo, a country suffering from a leadership vacuum, demands international recognition. Serbia, whose all-powerful president is facing violent protests, refuses to let it go.

The EU officials said no settlement between the two is possible without the U.S. and that American engagement is welcome. But they’ve been critical of the Trump administration, including Grenell, accusing the U.S. of going it alone and damaging years of diplomatic work with ad-hoc efforts aimed at scoring a quick win for Trump.

The Balkan jostling is a flashpoint in transatlantic tensions and underscores the growing chasm between the EU and Trump on issues ranging from trade to defense spending. It comes at a time when leaders such as Merkel are insisting that Europe forge its own path as strong post-World War II ties to the U.S. weaken.

Grenell, who served as the U.S. ambassador to Germany until last month, has rebuffed the accusation of quick-win diplomacy, saying that the U.S. is mainly focused on an economic settlement and would leave the political talks to the Europeans.

Grenell oversaw an agreement in February under which Serbia and Kosovo pledged to develop road and rail links to boost economic cooperation before resolving their long-lasting enmity. A month before, they signed a letter of intent to restore direct flights between their capitals, Belgrade and Pristina.

U.S. officials have also pointed to EU failures in foundering talks in recent years -- and the fact that five EU members don’t recognize Kosovo’s sovereignty.

“We have never believed in a quick election-year deal between Kosovo and Serbia,” Grenell said in a series of tweets early Wednesday embracing the EU initiative. “And we never thought our sole focus on economic normalization would be a quick fix.”

Still, Europeans have taken a dim view of U.S. overtures, viewing the Trump administration as treading on territory previously occupied by Merkel, who’s championed EU expansion in the Balkans. Last month, Merkel’s office and the EU’s special envoy, Miroslav Lajcak, responded with a flurry of shuttle diplomacy.

©2020 Bloomberg L.P.